Involvement of cholesterol efflux pathway in the control of cardiomyocytes cholesterol homeostasis

2012 ◽  
Vol 53 (2) ◽  
pp. 196-205 ◽  
Author(s):  
Anne Reboulleau ◽  
Véronique Robert ◽  
Benoît Vedie ◽  
Aline Doublet ◽  
Alain Grynberg ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Cholesterol Homeostasis ◽  
Efflux Pathway

scholarly journals Lipoprotein Lipase Regulates Microglial Lipid Droplet Accumulation

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 198
Author(s):  
Bailey A. Loving ◽  
Maoping Tang ◽  
Mikaela C. Neal ◽  
Sachi Gorkhali ◽  
Robert Murphy ◽  
...  
Keyword(s):  
Lipoprotein Lipase ◽  
Cholesterol Efflux ◽  
Acid Oxidation ◽  
Lipid Uptake ◽  
Expression Of Genes ◽  
Ppar Signaling ◽  
Ppar Agonists ◽  
Inflammatory State ◽  
Excessive Secretion ◽  
Efflux Pathway

Microglia become increasingly dysfunctional with aging and contribute to the onset of neurodegenerative disease (NDs) through defective phagocytosis, attenuated cholesterol efflux, and excessive secretion of pro-inflammatory cytokines. Dysfunctional microglia also accumulate lipid droplets (LDs); however, the mechanism underlying increased LD load is unknown. We have previously shown that microglia lacking lipoprotein lipase (LPL KD) are polarized to a pro-inflammatory state and have impaired lipid uptake and reduced fatty acid oxidation (FAO). Here, we also show that LPL KD microglia show excessive accumulation of LD-like structures. Moreover, LPL KD microglia display a pro-inflammatory lipidomic profile, increased cholesterol ester (CE) content, and reduced cholesterol efflux at baseline. We also show reduced expression of genes within the canonical cholesterol efflux pathway. Importantly, PPAR agonists (rosiglitazone and bezafibrate) rescued the LD-associated phenotype in LPL KD microglia. These data suggest that microglial-LPL is associated with lipid uptake, which may drive PPAR signaling and cholesterol efflux to prevent inflammatory lipid distribution and LD accumulation. Moreover, PPAR agonists can reverse LD accumulation, and therefore may be beneficial in aging and in the treatment of NDs.

Abstract: P444 TRANS INTESTINAL CHOLESTEROL EFFLUX PATHWAY IS NOT MEDIATED THROUGH HDL

2009 ◽  
Vol 10 (2) ◽  
pp. e754
Author(s):  
C Vrins ◽  
M van Eck ◽  
R Ottenhoff ◽  
P Rensen ◽  
A Groen
Keyword(s):  
Cholesterol Efflux ◽  
Efflux Pathway

scholarly journals Regulation of Cholesterol Homeostasis by the Liver X Receptors in the Central Nervous System

2002 ◽  
Vol 16 (6) ◽  
pp. 1378-1385 ◽  
Author(s):  
Karl D. Whitney ◽  
Michael A. Watson ◽  
Jon L. Collins ◽  
William G. Benson ◽  
Tammy M. Stone ◽  
...  
Keyword(s):  
Gene Expression ◽  
Central Nervous System ◽  
Nervous System ◽  
Cholesterol Efflux ◽  
Target Genes ◽  
Cholesterol Homeostasis ◽  
Neuronal Cultures ◽  
Primary Neuronal Cultures ◽  
The Central Nervous System ◽  
Lxr Agonists

Abstract The nuclear oxysterol receptors liver X receptor-α [LXRα (NR1H3)] and LXRβ (NR1H2) coordinately regulate genes involved in cholesterol homeostasis. Although both LXR subtypes are expressed in the brain, their roles in this tissue remain largely unexplored. In this report, we show that LXR agonists have marked effects on gene expression in murine brain tissue both in vitro and in vivo. In primary astrocyte cultures, LXR agonists regulated several established LXR target genes, including ATP binding cassette transporter A1, and enhanced cholesterol efflux. In contrast, little or no effect on gene expression or cholesterol efflux was detected in primary neuronal cultures. Treatment of mice with a selective LXR agonist resulted in the induction of several LXR target genes related to cholesterol homeostasis in the cerebellum and hippocampus. These data provide the first evidence that the LXRs regulate cholesterol homeostasis in the central nervous system. Because dysregulation of cholesterol balance is implicated in central nervous system diseases such as Alzheimer’s and Niemann-Pick disease, pharmacological manipulation of the LXRs may prove beneficial in the treatment of these disorders.

Abstract 5: Lipid Droplet Associated Hydrolase: A New Player in Cholesterol Mobilization From Foam Cells

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Younghwa Goo ◽  
Pradip Saha ◽  
Larry Chan ◽  
Antoni Paul
Keyword(s):  
Lipid Droplet ◽  
Cholesterol Efflux ◽  
Bone Marrow Cells ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Foam Cells ◽  
Peritoneal Macrophages ◽  
Cholesterol Homeostasis

Lipid laden macrophages/foam cells are a hallmark of atherosclerotic lesions from early to late stages of development. Macrophages take-up modified low-density lipoprotein (mLDL) particles and store surplus mLDL-derived cholesterol as cholesterol ester (CE) in cytoplasmic lipid droplets (LDs). Accelerating CE hydrolysis from the LDs is a plausible strategy to promote reverse cholesterol transport from the atheroma. However, the identity of the CE hydrolases that function on LDs remains unknown. Previously we identified lipid droplet-associated hydrolase (LDAH) in LDs purified from macrophages and reported that in vitro LDAH regulates CE levels by increasing CE hydrolysis. To determine the relevance of LDAH in atherogenesis, we have generated LDAH knockout (LDAH-/-) mice. Mouse peritoneal macrophages (MPM) isolated from LDAH-/- mice had increased cytoplasmic LDs, increased net CE content, and decreased cholesterol efflux. In atherosclerosis studies, both male and female LDAH-/- mice crossed with apolipoprotein E knockout (apoE-/-) mice fed a Western diet developed larger lesions. Lesions of LDAH-/-/ apoE-/- mice were characterized by increased areas of macrophages containing enlarged cytoplasms with large LDs. Supporting a direct atheroprotective role of LDAH in macrophages, lesions of apoE-/- mice that received bone marrows from LDAH-/-/apoE-/- mice progressed faster than those that received bone marrow cells from LDAH+/+/apoE-/- mice. In qPCR analyses of genes involved in cholesterol homeostasis in macrophages, we found that ABC binding cassette transporters ABCA1 and ABCG1, which mediate cholesterol efflux through the plasma membrane, were consistently decreased in LDAH-/- MPM. Further in vivo gene expression studies on macrophages selectively obtained from lesions using laser capture microdissection are underway. In conclusion, our study suggests that LDAH promotes LD CE hydrolysis and cholesterol efflux from foam cells within the atheroma, and uncovers a potential target to promote reverse cholesterol from arteries as a means of ameliorating atherosclerosis development.

scholarly journals Conditional Disruption of the Peroxisome Proliferator-Activated Receptor γ Gene in Mice Results in Lowered Expression of ABCA1, ABCG1, and apoE in Macrophages and Reduced Cholesterol Efflux

2002 ◽  
Vol 22 (8) ◽  
pp. 2607-2619 ◽  
Author(s):  
Taro E. Akiyama ◽  
Shuichi Sakai ◽  
Gilles Lambert ◽  
Christopher J. Nicol ◽  
Kimihiko Matsusue ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Gene Knockout ◽  
Critical Role ◽  
Density Lipoprotein ◽  
Cholesterol Homeostasis ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Exon 2 ◽  
Transgenic Mouse Line ◽  
Pparγ Gene

ABSTRACT Disruption of the peroxisome proliferator-activated receptor γ (PPARγ) gene causes embryonic lethality due to placental dysfunction. To circumvent this, a PPARγ conditional gene knockout mouse was produced by using the Cre-loxP system. The targeted allele, containing loxP sites flanking exon 2 of the PPARγ gene, was crossed into a transgenic mouse line expressing Cre recombinase under the control of the alpha/beta interferon-inducible (MX) promoter. Induction of the MX promoter by pIpC resulted in nearly complete deletion of the targeted exon, a corresponding loss of full-length PPARγ mRNA transcript and protein, and marked reductions in basal and troglitazone-stimulated expression of the genes encoding lipoprotein lipase, CD36, LXRα, and ABCG1 in thioglycolate-elicited peritoneal macrophages. Reductions in the basal levels of apolipoprotein E (apoE) mRNA in macrophages and apoE protein in total plasma and high-density lipoprotein (HDL) were also observed in pIpC-treated PPARγ-MXCre+ mice. Basal cholesterol efflux from cholesterol-loaded macrophages to HDL was significantly reduced after disruption of the PPARγ gene. Troglitazone selectively inhibited ABCA1 expression (while rosiglitazone, ciglitazone, and pioglitazone had little effect) and cholesterol efflux in both PPARγ-deficient and control macrophages, indicating that this drug can exert paradoxical effects on cholesterol homeostasis that are independent of PPARγ. Together, these data indicate that PPARγ plays a critical role in the regulation of cholesterol homeostasis by controlling the expression of a network of genes that mediate cholesterol efflux from cells and its transport in plasma.

scholarly journals Liver X Receptor β (LXRβ) Interacts Directly with ATP-binding Cassette A1 (ABCA1) to Promote High Density Lipoprotein Formation during Acute Cholesterol Accumulation

2011 ◽  
Vol 286 (22) ◽  
pp. 20117-20124 ◽  
Author(s):  
Masako Hozoji-Inada ◽  
Youichi Munehira ◽  
Kohjiro Nagao ◽  
Noriyuki Kioka ◽  
Kazumitsu Ueda
Keyword(s):  
Translational Regulation ◽  
Cholesterol Efflux ◽  
Density Lipoprotein ◽  
Transcriptional Response ◽  
Liver X Receptor ◽  
Cholesterol Homeostasis ◽  
Atp Binding ◽  
Transcriptional Level ◽  
Cholesterol Accumulation ◽  
Atp Binding Cassette

Cells have evolved multiple mechanisms for maintaining cholesterol homeostasis, and, among these, ATP-binding cassette protein A1 (ABCA1)-mediated cholesterol efflux is highly regulated at the transcriptional level through the activity of the nuclear receptor liver X receptor (LXR). Here, we show that in addition to its well defined role in transcription, LXRβ directly binds to the C-terminal region (2247LTSFL2251) of ABCA1 to mediate its post-translational regulation. In the absence of cholesterol accumulation in the macrophage-like cell line THP-1, the ABCA1-LXRβ complex stably localizes to the plasma membrane, but apolipoprotein A-I (apoA-I) binding or cholesterol efflux does not occur. Exogenously added LXR ligands, which mimic cholesterol accumulation, cause LXRβ to dissociate from ABCA1, thus freeing ABCA1 for apoA-I binding and subsequent cholesterol efflux. Photoaffinity labeling experiments with 8-azido-[α-32P]ATP showed that the interaction of LXRβ with ABCA1 inhibits ATP binding by ABCA1. This is the first study to show that a protein-protein interaction with the endogenous protein suppresses the function of ABC proteins by inhibiting ATP binding. LXRβ can cause a post-translational response by binding directly to ABCA1, as well as a transcriptional response, to maintain cholesterol homeostasis.

scholarly journals Cholesterol, Oxysterols and LXRs in Breast Cancer Pathophysiology

2020 ◽  
Vol 21 (4) ◽  
pp. 1356
Author(s):  
Hassan Nazih ◽  
Jean Marie Bard
Keyword(s):  
Breast Cancer ◽  
Cholesterol Efflux ◽  
Biological Effects ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
High Growth ◽  
High Growth Rate ◽  
Tumor Formation ◽  
Cholesterol Homeostasis ◽  
Density Lipoprotein Receptor

Breast cancer is the most frequent cancer among women. In 2018, it is estimated that 627,000 women died from breast cancer. This is approximately 15% of all cancer deaths among women (WHO 2018). Breast cancer is a multifactorial chronic disease. While important progress has been made to treat patients, many questions regarding aspects of this disease relating to carcinogenesis are still open. During carcinogenesis, cells exhibit cholesterol homeostasis deregulation. This results in an accumulation of intracellular cholesterol, which is required to sustain their high growth rate. Cholesterol efflux and influx are two metabolic pathways that are necessary to prevent cholesterol accumulation in the cells. Liver X receptors (LXRs) are nuclear receptors that, upon activation, induce the expression of ABC transporters, responsible for promoting cholesterol efflux, and the expression of IDOL (inducible degrader of low-density lipoprotein receptor), in charge of reducing cholesterol influx. Oxysterols, oxygenated derivatives of cholesterol formed through different pathways, have been discovered as LXR-specific ligands. Some oxysterols are involved in tumor formation while others are considered anti-tumor agents. In the present review, we discuss the involvement of cholesterol, oxysterols and LXRs in breast cancer pathophysiology, with an emphasis on the biological effects of LXR ligands.

Abstract 403: Identification of CHROME as a Competing Endogenous RNA that Regulates Cholesterol Homeostasis

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Coen van Solingen ◽  
Elizabeth J Hennessy ◽  
Mireille Ouimet ◽  
Kaitlyn Rinehold ◽  
Maryem Hussein ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Target Genes ◽  
Hdl Cholesterol ◽  
Cholesterol Homeostasis ◽  
Competing Endogenous Rna ◽  
Cellular Cholesterol ◽  
Expression Of Genes ◽  
Non Coding Rna ◽  
Non Coding Rnas ◽  
X Receptors

The discovery of microRNAs (miRNA) targeting gene pathways involved in HDL and LDL metabolism illuminated the potent role of non-coding RNAs in the regulation of cholesterol homeostasis. Long non-coding RNAs (lncRNA) have also been identified as crucial regulators of gene expression; however, few have been fully characterized. Here we report a novel human lncRNA, CHROME (Cholesterol Homeostasis Regulator Of MicroRNA Expression), that functions as a competing endogenous RNA to regulate cellular cholesterol homeostasis. We show that CHROME has 7 broadly expressed variants that are transcriptionally regulated by the cholesterol-sensing liver X receptors. Computational analyses revealed that CHROME harbors binding sites for multiple (11) miRNAs involved in cholesterol homeostasis, including miR-27b and miR-33a/b, which function as hubs controlling the expression of genes involved in cholesterol efflux and HDL metabolism. Using CHROME knock-down and overexpression, we demonstrate that CHROME acts as a ‘miRNA sponge’ that sequesters these miRNAs, limiting their ability to repress target genes, including ABCA1, OSBPL6 and ANGPTL3. Consistent with this, we show that overexpression of CHROME increases cholesterol efflux, whereas its silencing reduces cholesterol efflux from primary human hepatocytes and macrophages. As hepatic cholesterol efflux via ABCA1 plays a central role in HDL biogenesis, we investigated the relationship of CHROME to its miRNA targets and plasma levels of HDL cholesterol in liver samples from a cohort of 200 healthy individuals. This analysis showed that CHROME is inversely correlated with miR-27b and miR-33a/b levels, and positively correlated with levels of their target genes and plasma HDL cholesterol. Collectively, these findings identify CHROME as a key regulatory component of the non-coding RNA circuitry that controls cellular cholesterol efflux and plasma HDL levels in humans.

Abstract 255: Plasminogen Promotes Cholesterol Efflux by the ABCA1

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Nathalie Pamir ◽  
David A Dichek ◽  
Godfrey S Getz ◽  
Santica Marcovina ◽  
Jay W Heinecke
Keyword(s):  
Size Exclusion Chromatography ◽  
Cholesterol Efflux ◽  
Particle Concentration ◽  
Specific Activity ◽  
Cholesterol Homeostasis ◽  
Size Exclusion ◽  
Spectrometric Analysis ◽  
Cvd Risk ◽  
Exclusion Chromatography

Background: The cholesterol efflux capacity (CEC) of serum HDL, measured using cultured macrophages predicts incident and prevalent CVD risk in humans. The ABCA1 pathway is a key regulator of macrophage cholesterol homeostasis in vivo. Methods: We used genetic and biochemical approaches in mice to identify important mediators of CEC. Results: On high-resolution size-exclusion chromatography of mouse plasma, macrophage CEC and HDL co-eluted as a single major peak, suggesting that HDL mediates cholesterol efflux. In contrast, size-exclusion chromatography revealed two major peaks of material that promoted ABCA1-specific CEC, one of which was distinct from HDL. HDL particle concentration was reduced by 75% in Apoa1 -/- mice; this resulted in a 50% decrease in macrophage CEC but, surprisingly, had no impact on ABCA1-specific CEC. Orthogonal chromatography-mass spectrometric analysis of the non-HDL-associated efflux inducing material isolated from wild-type and APOA1 deficient plasma showed that plasminogen strongly correlated with ABCA1-specific CEC. Moreover, isolated plasminogen promoted cholesterol efflux by the ABCA1 pathway, and the specific activity of ABCA1-specific CEC of non-HDL-associated material was reduced by 50% in plasminogen deficient plasma. Imaging of cells treated with fluorescently-labeled antibodies demonstrated that ABCA1 and plasminogen co-localized on the plasma membrane. Conclusions: HDL particle concentration is an important contributor to macrophage CEC. However, other pathways contribute to ABCA1-specific CEC; our studies identify plasminogen as one potential mediator. Plasminogen associates with CVD risk in human genetic studies, raising the possibility that it plays a role in atherosclerosis by modulating ABCA1-mediated sterol efflux from macrophages.

Abstract 533: Salicylate Restores Macrophage Cholesterol Homeostasis via Activation of AMP-Activated Protein Kinase

2015 ◽  
Vol 35 (suppl_1) ◽  
Author(s):  
Morgan D Fullerton ◽  
Chelsea P McGregor ◽  
Nicholas D LeBlond ◽  
Shayne A Snider ◽  
Rebecca J Ford ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cholesterol Efflux ◽  
Inflammatory Responses ◽  
Therapeutic Potential ◽  
Foam Cell ◽  
Cholesterol Homeostasis ◽  
Dependent Manner ◽  
Cholesterol Uptake ◽  
Gene And Protein Expression ◽  
Amp Activated Protein Kinase

Objectives: Atherosclerosis stems from imbalances in lipid metabolism and leads to maladaptive inflammatory responses. AMP-activated protein kinase (AMPK) is a highly conserved serine/threonine kinase that regulates many aspects of lipid and energy metabolism, although its specific role in controlling macrophage foam cell cholesterol homeostasis remains unclear. Methods: We sought to address this question by testing the effects of AMPK-specific activators in primary bone marrow-derived macrophages from AMPK β1-deficient (β1-/-) mice. Results: Macrophages from AMPK β1-/- mice had enhanced lipogenic potential and diminished cholesterol efflux, although cholesterol uptake was unaffected. Specific activation of Ampk β1 via salicylate (the unacetylated form of aspirin) or A-769662 (a small molecule activator), decreased the synthesis of both fatty acids and sterols in WT but not AMPK β1-/- macrophages. In lipid-laden macrophage foam cells, salicylate and A-769662 decreased cholesterol uptake and increased cholesterol efflux to HDL and apoA-I, effects that occurred in an AMPK β1-dependent manner. Increased cholesterol efflux was also associated with increased gene and protein expression of the ATP binding cassette transporters, ABCG1 and ABCA1. Moreover, in vivo reverse cholesterol transport was significantly suppressed in mice that received AMPK β1-/- macrophages compared to WT control. Conclusion: Our data highlight the therapeutic potential of targeting macrophage AMPK with new or existing drugs for the restoration of cholesterol homeostasis during the early stages of atherosclerosis.

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